This study will evaluate the survival of leukocyte transfusions by use of DFP-labeled leukocytes and will utilize specific parameters of leukocyte metabolism to evaluate the effective survival of the leukocyte in transfusion recipients. Platelet survival data will be obtained by the use of 51Cr labeled donor platelets and physiological survival of platelets as evidenced by a coagulation survey: 1. To evaluate the use of histocompatible, i.e., ABO-Rh and HL-A matched donors in the maintenance and support of patients with marrow hypoplasia. 2. To evaluate the functional survival of the cellular components in the leucocyte-platelet transfusion preparations and in the recipient following transfusion. 3. Specific interest is warranted in the evaluation of leukocytes from the donor with polycythemia vera. It is established that these leukocytes are metabolically hyperactive in phagocytic functions. 4. To compare the clinical course of patients supported by pooled platelet-leukocyte transfusions with those treated by a ssngle private histocompatible (HL-A-ABO-Rh) donor. 5. To evaluate effects of currenty used and selected investigational cancer chemotherapeutic agents on platelet function, especially in acute myelogenous leukemia. 6. To evaluate effects and interactions of drugs commonly used in leukemic patients as supportive concomitants to chemotherapy on platelet function. 7. To evaluate effects of platelet transfusion on platelet function in selected patients with acute myelogenous leukemia.